Expr.Struct (StructOps)

Namespace: Polars.CSharp

Operations on Struct columns. Access via Expr.Struct.

Properties & Indexers

Property	Type	Description
this[long index]	Expr	Retrieve a field by its index.
this[string name]	Expr	Retrieve one of the fields of this Struct as a new expr.
this[string[] name]	Expr	Retrieve a field from the struct by name.

Instance Methods

Drop

Drop one or more fields from the struct.

public Expr Drop(IEnumerable<string> names, bool strict = true)

Parameters

Name	Type	Description
names	IEnumerable<string>	Names of the fields to drop.
strict	bool	If True, raise an error if any of the specified fields do not exist in the struct.

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Field

Retrieve a field from the struct by name.

Retrieve a field by its index.

public Expr Field(params string[] name)
public Expr Field(long index)

Parameters

Name	Type	Description
name	string[]	The name of the field.
index	long	-

Example

var df = DataFrame.FromColumns(new
{
    id = new[] { 1, 2 },
    product = new[] 
    { 
        new { Name = "Laptop", Specs = new { Ram = 16, SSD = 512 } },
        new { Name = "Mouse",  Specs = new { Ram = 0,  SSD = 0   } }
    }
});

df.Select(
    Pl.Col("id"),
    Pl.Col("product").Struct.Field("Name").Alias("prod_name"),
    // Nested Access
    Pl.Col("product").Struct.Field("Specs").Struct.Field("Ram").Alias("ram_gb")
).Show();
/* Output:
shape: (2, 3)
┌─────┬───────────┬────────┐
│ id  ┆ prod_name ┆ ram_gb │
│ --- ┆ ---       ┆ ---    │
│ i32 ┆ str       ┆ i32    │
╞═════╪═══════════╪════════╡
│ 1   ┆ Laptop    ┆ 16     │
│ 2   ┆ Mouse     ┆ 0      │
└─────┴───────────┴────────┘
*/

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JsonEncode

Convert the struct column into a JSON string column. Useful for debugging or exporting to systems that support JSON strings.

public Expr JsonEncode()

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RenameFields

Rename the fields of the struct.

public Expr RenameFields(params string[] names)

Parameters

Name	Type	Description
names	string[]	The new names for the fields.

Example

df.Select(
    Pl.Col("product").Struct.RenameFields(["NewName", "NewSpecs"])
);

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Unnest

Expand the struct into its individual fields.Alias for Expr.Struct.field("*").

public Expr Unnest()

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WithFields

Add or overwrite fields of this struct.This is similar to with_columns on DataFrame.

public Expr WithFields(params IntoExprColumn[] fields)

Parameters

Name	Type	Description
fields	IntoExprColumn[]	-

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